Method for S/TEM sample analysis

Abstract

An improved method and apparatus for S/TEM sample preparation and analysis. Preferred embodiments of the present invention provide improved methods for TEM sample creation, especially for small geometry (<100 nm thick) TEM lamellae. Preferred embodiments of the present invention also provide an in-line process for S/TEM based metrology on objects such as integrated circuits or other structures fabricated on semiconductor wafer by providing methods to partially or fully automate TEM sample creation, to make the process of creating and analyzing TEM samples less labor intensive, and to increase throughput and reproducibility of TEM analysis.

We claim as follows: 
     
       1. A method of processing a semiconductor wafer, comprising:
 assigning the semiconductor wafer a wafer ID; 
 storing at least one recipe for sample extraction in a host processor; 
 selecting at least one recipe by a controller for the processing of the wafer, said recipe including positional data for one or more sample sites to be analyzed; 
 loading the wafer into a charged particle beam system, said charged particle beam system to process the wafer according to the selected process recipe values; 
 navigating to each sample site using said positional data; 
 imaging each sample site; 
 identifying at least one desired first fiducial location for said first sample site; 
 milling a combination of at least one high precision fiducial mark and one low precision fiducial mark at the desired first fiducial locations; 
 determining the edge positions for the sample with respect to said fiducial marks 
 automatically milling the wafer surface on either side of each desired sample location leaving a thin layer of material; 
 transferring the one or more samples to an ex-situ lamella extraction device, said device importing recipe values including positional data for each sample site; 
 extracting the one or more samples from the wafer using said recipe values; 
 transferring the one or more samples to a TEM system, said TEM importing recipe values for each sample and said TEM also processing the one or more samples according to the values specified by the recipe, said processing including imaging the samples and analyzing the images; 
 imaging the one or more samples with the TEM; 
 analyzing the TEM images to determine a feature dimension for the one or more sample sites; and 
 adjusting the positional data or fiducial mark locations at additional sample sites in response to the determined dimension. 
 
     
     
       2. The method of  claim 1  wherein navigating to a sample site using said positional data comprises automatically navigating to a sample site using said positional data. 
     
     
       3. The method of  claim 1  wherein milling the wafer surface on either side of the desired sample location leaving a thin vertical layer of material comprising a sample to be analyzed comprises automatically milling the wafer surface on either side of the desired sample location leaving a thin vertical layer of material comprising a sample to be analyzed. 
     
     
       4. The method of  claim 1  wherein extracting the samples from the wafer comprises automatically extracting the samples from the wafer. 
     
     
       5. The method of  claim 1  further comprising marking each wafer with a unique wafer ID. 
     
     
       6. The method of  claim 1  wherein transferring the one or more samples to a TEM system comprises loading the one or more samples onto a TEM sample holder, said sample holder mounted on a moveable mechanical TEM stage, and wherein imaging the one or more samples with the TEM further comprises automatically adjusting the position of said moveable stage so that each sample can be imaged at the same orientation and with the sample upper surface at the same height relative to the TEM column. 
     
     
       7. The method of  claim 6  wherein said automatic adjustment comprises:
 initially imaging the sample with the electron beam in the TEM; 
 using pattern recognition to identify the orientation of the sample and automatically moving the TEM stage so that each sample is properly rotate and center each sample so that each sample is imaged by the TEM at the same orientation relative to the TEM electron beam. 
 
     
     
       8. The method of  claim 6  wherein said automatic adjustment comprises:
 initially imaging the sample with the electron beam in the TEM; 
 using image processing to determine whether a TEM stage adjustment is necessary to ensure that all axes of the sample orientation are normal to the electron beam; and 
 making any necessary adjustment by moving the TEM stage.